Hyposensitivity is a form of Sensory Processing Disorder (SPD) that affects how the brain receives and interprets information from the senses. The nervous system responds less intensely or more slowly to sensory input compared to a neurotypical person. This under-responsivity means everyday stimuli, such as sights, sounds, or touch, may not register clearly. Hyposensitivity is the opposite of hypersensitivity, or sensory over-responsivity, which involves an exaggerated reaction to stimuli.
Understanding Sensory Under-Responsivity
The mechanism behind hyposensitivity involves a high neurological threshold for sensory input. This high threshold means the brain requires significantly greater intensity or duration of a stimulus before it registers the sensation and initiates a response. Since input is not registered efficiently, the individual may appear disengaged, unaware of their surroundings, or slow to react to stimuli.
This difficulty registering input causes “sensory seeking” behaviors, which are active attempts to compensate for the under-registration. The person seeks intense sensory experiences to push the input level high enough to cross their neurological threshold and achieve a functional level of arousal. This under-responsivity affects the five external senses—sight, sound, touch, taste, and smell—as well as the internal senses.
The internal senses of proprioception (awareness of body position and movement) and the vestibular system (balance and spatial orientation) are frequently impacted by this high threshold. When these systems are under-responsive, the brain struggles to process where the body is in space. This leads to a constant search for intense movement and deep pressure to provide necessary feedback.
Common Behavioral Indicators
The neurological mechanism of under-responsivity translates into a distinct set of observable behaviors. One common indicator is a high tolerance for pain, heat, or cold, where an individual may not notice an injury until it is pointed out. This reduced awareness of pain can pose safety risks, as the body’s natural warning system is muted.
Individuals often display a constant need for movement or excessive fidgeting to stimulate the under-responsive vestibular system. They might seek out activities like vigorous spinning, jumping, or rocking. A lack of proprioceptive input often results in clumsy behavior, such as accidentally bumping into objects or “crashing” into furniture and walls.
Sensory seeking extends to other senses through a craving for strong or intense input. This can manifest as speaking with excessive volume, listening to music at maximum levels, or enjoying strong smells. Individuals often prefer highly textured foods or very intense flavors, such as spicy, sour, or crunchy items, to register the sensation of taste and texture.
Origins and Associated Conditions
Hyposensitivity can exist as a standalone diagnosis within Sensory Processing Disorder (SPD), but it is frequently observed alongside other neurodevelopmental conditions. This under-responsivity is a recognized characteristic in individuals on the Autism Spectrum Disorder (ASD). The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) recognizes both hyper- and hyporeactivity to sensory input as a manifestation of restricted and repetitive behavior patterns in ASD.
Hyposensitivity is also commonly linked to Attention Deficit Hyperactivity Disorder (ADHD) and other general developmental delays. While the exact cause is often not fully known, research suggests it results from neurological differences in how the brain processes and integrates sensory input. Genetic factors and family history of SPD, ASD, or ADHD are considered risk factors, alongside environmental influences such as premature birth or early environmental deprivation.
Strategies for Sensory Input
The primary therapeutic approach for managing hyposensitivity is Occupational Therapy (OT). An occupational therapist conducts an assessment to create an individualized plan designed to meet the high sensory threshold. This plan often includes a “sensory diet,” a structured schedule of sensory activities incorporated throughout the day to help the individual maintain an optimal state of arousal.
A sensory diet focuses on providing high-intensity, purposeful activities that stimulate the nervous system. Strategies frequently involve heavy work tasks, which provide strong proprioceptive input, and movement-based activities for the vestibular system. The goal is to provide necessary sensory feedback in a controlled, consistent manner, helping the individual better process information and participate more fully in daily life.
Specific Sensory Strategies
Strategies for stimulating the nervous system include:
- Heavy work tasks, such as pushing, pulling, or carrying weighted objects, to provide strong proprioceptive input.
- Deep pressure input, often delivered through therapeutic hugging, weighted vests, or weighted blankets, to help the nervous system regulate and improve body awareness.
- Movement-based activities for the vestibular system, such as jumping on a trampoline, swinging, or bouncing on a therapy ball, which provide high-intensity input.